docs: def edge_val_dump(self):
          """Yield the entire contents of the edge_val table."""
          self._flush_edge_val()
          for (
                  graph, orig, dest, idx, key, branch, turn, tick, value
          ) in self.sql('edge_val_dump'):
              yield (
                  self.unpack(graph),
                  self.unpack(orig),
                  self.unpack(dest),
                  idx,
                  self.unpack(key),
                  branch,
                  turn,
                  tick,
                  self.unpack(value)
              )